RESUMO
Duckweeds have long been consumed as vegetables in several South Asian countries. In this study of the chemical constituents of duckweed Landoltia punctata, a new compound, apigenin 6-C-[ß-D-apiofuranosyl-(1 â 2)]-ß-D-glucopyranoside (1), and a previously LC-MS identified compound, quercetin 3-O-ß-D-apiofuranoside (3), as well as three known compounds, luteolin 6-C-[ß-D-apiofuranosyl-(1 â 2)]-ß-D-glucopyranoside (2), apigenin 6-C-ß-D-glucopyranoside (4), and luteolin 7-O-neohespirodise (5), were isolated and identified on the basis of MS and NMR spectroscopic analyses and chemical derivations. In total, 24 flavonoids were identified in L. punctata 0001 by UPLC-ESI-QTOF-MS2. In DPPH and ABTS assays, 3 exhibited significant antioxidant activity with IC50 values of 4.03 ± 1.31 µg/mL and 14.9 ± 2.28 µg/mL, respectively. In in vivo antioxidant activity assays, 1 significantly increased the survival rate of juglone-exposed Caenorhabditis elegans by 2 to 3-fold, and by 75% following thermal damage. Compounds 1-5 exhibited moderate scavenging capacities of intracellular reactive oxygen species in C. elegans exposed to H2O2.